The objective of the parent study is to investigate possible causal mechanisms associated with an increased incidence of idiopathic pulmonary hemosiderosis in a geographic cluster area in the eastern Cleveland metropolitan area. In the process of the investigation by the Centers for Disease Control and Prevention, several lines of evidence point toward an etiological role of mycotoxins from an unusual fungus, Stachybotrys chartarum. Extensive environmental sampling of patient and control homes, done by NIOSH, found this fungus in all but one of the 12 patient homes studied and in 16 of 29 control subject homes. The purpose of this addendum involving the GCRC is to further investigate control subjects who are at-risk for pulmonary hemosiderosis due to Stachybotrys in their homes. Follow-up visits of all affected infants continue. New subjects are included at the time of diagnosis. The current cohort of 39 affected babies includes 12 deaths and 3 lost of follow-up. Dr. Dearborn's laboratory is developing two new quantitative tests applicable to airborne sampling. Neither of these tests are being or will be used in the near future to make public health decisions regarding these infants and their families.